This thread, quoting some of the world's finest framebuilders, gives some pretty persuasive arguments for using lugs. I thought it interesting enough to copy and paste it into a Word document.

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Froze --

Peter you’re incorrect about the heat zone being less in TIG welding. Here is a quote from Airborne Bicycles concerning what you said:

"How you weld a standard metal frame together is very important. For steel you can use lugs, TIG welding, or fillet brazing. Lugs add weight, TIG welding is good on weight but it actually melts the tubes that are being put together and creates a heat affected zone (HAZ) in the tubes that may eventually lead to a failure. The fillet brazing uses a brass-silver “glue” that gets melted in to hold the tubes together. This is actually the best system, since the tubes don’t form this HAZ, and the braze is strong enough to hold it all together. For aluminum, the most common practice is TIG welding, and most Aluminum frames will fail at the welds due to the HAZ in the tubes. Ti is also TIG welded, and has the same problems as Aluminum. However, especially in Ti 6-4 you can find frames that are welded with commercially pure Ti (CP) instead of Ti 6-4, and therefore this acts like a fillet braze”. In theory these frames are stronger since the HAZ is smaller in the Ti tubes as the CP Ti brazing material melts at a lower temperature than the 6-4 Ti tubes, so the tubes are never melted in the welding process."

Then there's the following from Rivendell:

"Methods of construction: Brazing a frame with lugs is the most time-consuming way to make a frame, and is the least popular, and generally least sought-after way. So those who do it are either fools or have good reasons. A properly designed and built lugged steel frame is the strongest and most beautiful. It ought to also be the most expensive by far, but often isn’t.

Brazed, with lugs: Pro: Makes the strongest joints. Simplifies tube replacement, so a crashed frame needn't be thrown away. Arguably the most interesting joints, since lugs are available in a variety of styles, and offer the craftsman more creative options.

Con: It's takes more time, therefore it costs more; and there's a shortage of good brazers. The lugs have to more or less match the joints, and many modern "high tech downhill" style bikes have joints that nobody makes lugs for.

TIG-welded: Pro: Fast, economical, strong, and versatile. Any tube configuration can be TIG-welded, because there are no lugs to deal with.

Con: High heat levels are concentrated at the most stressed area of the frame. Melts the underlying tube, making tube replacement impractical-to-impossible.

What is a lug? A sleeve of metal that surrounds the frame tube at the joint, strengthening the joint. Most modern frames don't have them.

2. How come? They're more expensive to build with; and from a strictly practical point of view, they're unnecessary.

3. What does a lug do? It strengthens the joint by adding material to the stressed areas, and distributes the stresses over a large area. And it adds an artistic element to the frame joint. And it allows tubes to be joined by brazing, rather than welding.

4. Why brazing rather than welding? Less heat, mainly, and one of the benefits is that the tubes themselves are not melted. So, if you crash and bend a top tube, for instance, it can be replaced and the frame made good as new.

5. Are all lugs alike? No. Some are well-designed to eliminate stresses. Others cause stresses. Some are thick, some are thin. Some fit the tubes well, others don't. Some are rather plain, some are rather ostentatious. Some are generic and available for purchase by anybody, others are proprietary and unique to one brand of bike. Some are hand-cut and one-of-a-kind. In addition, lugs can be made by any of several methods, including but not limited to investment casting, stamping and welding, die casting, and machining.

6. Is there any reason to get a lugged frame over a glued or TIG-welded frame? Well, it depends. From strictly a functional perspective, in the short-term life of a bicycle, it makes no difference whether the frame is lugged or not. And, if you plan to get a new frame every couple of years, then the long-term benefits of a lugged frame (durability and the ability to replace bent/crashed tubes) don't work for you. Likewise, if you prefer the appearance of TIG-welds, then you won't be talked into lugs, no matter what."

Then there's this from Henry James:

"Steel is the only metal that can economically and technically be used with lugs. These simple sockets at each frame tube joint reinforce the joint to improve strength, reliability and (fatigue) life. Silver or brass brazing completes the structure with minimal metallurgical damage (unlike welding which must melt the metal under essentially uncontrolled conditions). The hype put out by aluminum and titanium makers is that welding is stronger, lighter, the latest technology, and magically better. In fact, they can't use lugs and have no choice but to weld, and so they turn to hype..."

Then there's this from Kirk Frames:

"Kirk frames are made exclusively of brazed steel. I use steel because it offers many advantages, including: Ride quality, Fatigue resistance, availability of tubes with a wide variety of specs, Cost and Reparability. Steel's combination of stiffness and fatigue resistance allows smaller diameter tubing compared to titanium or aluminum. Tubing diameter is one of the main factors that influences ride quality. For example, aluminum tubing needs to be large in diameter due to its poor fatigue resistance. Titanium, on the other hand, is much more flexible than steel so it needs to be large in diameter to be stiff enough to handle properly and transfer energy. Steel tubing offers a balance of a supple ride and durability that make it a choice building material.

Brazing: Traditional brazed joints are the choice for Kirk frames. Some advantages of brazed joints are: Lower heat compared to welded joints, Smaller heat-affected zone, Allows for the use of thinner tubing and Aesthetic qualities. Brazing heats the steel to about 1,800 degrees F - just hot enough to allow the brass or silver to melt and flow into the joint. Welding, by contrast, heats the tubing to its melting point (around 3,500 degrees F). At this temperature annealing occurs in most tubing, causing a weakened area adjacent to the joint. Brazing allows for a much smaller heat-affected zone than welding. The use of lugs or fillets spreads the load over a larger area than a welded joint. This can allow the builder to use thinner tubing for a given size rider, without risking failure."

And there's Spectrum Cycles:

"Our steel frames are lugged for two reasons. Lugs are stronger and lugs are beautiful. Did we mention that lugs are stronger? Almost all mass-production steel frames produced today utilize cost-effective TIG welding to join tubes. This prompts a question: why do we still use silver soldered lugged joining? Because properly fitted and soldered lugged joints are considerably stronger than joints created any other way.

On Strength: In the late '80s, a team of scientists in the UC Davis engineering department undertook an in-depth look at the relative strengths of various steel joining techniques at the request of "Bicycle Guide" magazine. The three top frame builders associated with the three primary joining techniques were asked to supply joining samples using tubing supplied to the builders from the same mill run. Tom Ritchie provided the fillet-brazed samples, TIG-welding was done by Gary Helfrich, and the silver soldered lugged samples were done by Spectrum's Jeff Duser. The samples were fatigue tested, in some cases to failure. In most cases, the joints did not fail. More often, the tubes failed at or near the joint. The team's study involved microscopic analysis of the crystal structure of joining zones, heat effected zones and failure sites. They concluded that all three joining techniques, done properly, are clearly of sufficient strength for the purpose of bicycle frame construction. The different results obtained from the samples resulted primarily in the heat-affected areas of the tubes themselves. Not surprisingly, the tubes that were soldered turned out to be stronger than the tubes that were welded or brazed. So, what does this mean in the real world? Frames built with silver soldered lugs will last longer than those that are fillet brazed and considerably longer than those that are welded. However, for most of our customers, the real practical difference is that lugged frames hold up in crashes better, and when it becomes necessary, they are much easier to repair. On Modern Air Hardening Tubing: The latest generation of air-hardening steel tubing used by top quality welding frame builders was not available at the time of the UC Davis study. We at Spectrum expect that this tubing, when in the hands of master builders, is more reliable than the welded joints and tubes tested at UC Davis but still less strong than lugged joints.

Then let's not forget the master Richard Sachs:

"Most of the racing bikes you see today use mass-produced frames made out of carbon fiber (light, but extremely delicate), aluminum (light, but delicate and brittle to ride) and titanium (light and durable, but aesthetically crude). Because of economic reasons, the handmade lugged steel bicycle frame has become practically extinct. In the long run it's much less labor intensive to create molded carbon fiber frames or TIG welded aluminum frames than it is to join steel tubes together with a 56% silver brazing compound and a set of lugs.

Amazing how most of America's best frame builders still swear by lugs and brazing...why? Because they’re locked in the past? Refuse to grow up with the technology? Stubborn refusal to comply? NO!!! Their reputations are on the line for all the bikes they make, and if they felt welding was superior they would ALL be doing it!!!!!

Dave Kirk –

This is an interesting thread and got me to thinking (scary I know). What is the real weight difference between lugged and TIGged. It of course matters what lugs are being used (some are lighter than others) and the tubes and such.

Well I went into the vast "Kirk Frameworks center of weights and measures" and broke out the kitchen scale and came up with some interesting numbers. My idea was to weigh the frame components that differ when building a lugged versus TIG bike. They are-

Seat tube - on a lug bike it needs a seat lug of course but it doesn't need an externally butted seat tube (reinforced with a heavier wall at the top to handle the clamping duties). The TIG bike also needs a slip on clamping collar.

Bottom bracket - both types use a bb shell of course but the lugged shell has more to it so the weight differs.

Head tube - a lugged bike has....head lugs while a TIG bike does not. But the TIG bike has a heaver walled tube to deal with the loads and headset stress.

TIG welding rod versus brazing rod - a really tough one to estimate. I'm calling it a wash. I'm sure there is of course a difference but it can't amount to much. I'd guess that the brazing rod is a bit heavier and for the academic exercise of it all I'm going to research into this and find out some real numbers. But as stated above it can't amount to much as neither rod weighs much to begin with.

The measurements were taken on Reynolds 725 tubes that were the same length. The lugs are standard Richie Sachs lugs. Weight is in grams.


TIG

seat tube - 350
BB shell - 100
head tube - 175
seat tube clamp - 25

total 650


LUG

seat tube 275
long shen BB shell 140
HT and lugs 180
seat tube clamp N/A 0

total 595



Now I can here the screaming out there (sssshhh!). I fully understand that my kitchen scale is not the most accurate device known to man but it's fine for a comparison I think. I fully recognize that this is a bit crude and that the brazing rod might add a few grams the lug side of the equation but anyway you cut it the weight difference between a TIG and lug bike is minimal and might even favor the lugs bike by a few grams.

I think that this is in line with what we see available out there.....a good steel frame weighs about 3.5 to 3.75lbs no matter how you put it together.

Let the flaming begin!

Dave